1. Field of the Invention
The present invention relates to a rangefinder apparatus for measuring the distance to an object; and, in particular, to an active type rangefinder apparatus suitably used in a camera or the like.
2. Related Background Art
In active type rangefinder apparatus used in cameras and the like, a light-projecting section projects a beam toward an object to be measured (object to be photographed), the part of beam reflected by the object is received by a position sensitive detector (PSD) in a light-receiving section, and the distance to the object is measured (range-finding is effected) according to a signal outputted from the PSD. FIG. 1 is a view showing an arrangement of the front face of a camera. As depicted, a finder 9 and a lens mount 8A holding a taking lens 8 are disposed in the front face portion of the camera body. As a rangefinder apparatus, a light-projecting device 4 and a PSD 5 are disposed in alignment with the sidewise direction, i.e., base-length direction 50, on the upper side of the lens mount 8A.
FIGS. 2A and 2B are explanatory views of range-finding by the light-projecting device 4 and PSD 5. As shown in FIG. 2A, when the object to be measured is located at position P.sub.1, then the reflected light of the beam projected to the object from the light-projecting device 4 is received, by way of a light-receiving lens 5A, at position p.sub.1 on the PSD 5. When the object is located at position P.sub.2, then the reflected light of the beam projected to the object from the light-projecting device 4 is received, by way of the light-receiving lens 5A, at position p.sub.2 on the PSD 5. Then, as shown in FIG. 2B, the center-of-gravity position 400 of the beam 300 received by the PSD 5 is detected, and the distance to the object is detected according to thus detected center-of-gravity position 400.